1. Field of the Invention
This invention relates generally to reducing aerodynamic drag and is directed particularly to reducing air drag imposed on the frontal surface of trailers being towed by tractors of the large tractor-trailer rig type.
2. Description of the Prior Art
Tractor-trailer rigs on the highways are faced with directly striking air currents which impinge against the forward walls of the trailers. These currents become increasingly greater as the speed of the vehicle increases. Prior attempts to reduce the drag caused by these currents have met with partial success. U.S. Pat. No. 3,695,673 describes an air deflector comprising a generally plow-shaped shield affixed to the roof of the tractor. Each side panel of this patented deflector presents a single concave surface which defines a valley extending from the base of the deflector upwardly to the top edge of the deflector. U.S. Pat. No. 3,947,065 describes a similar plow-shaped deflector which has a pair of concave side panels with the concavity of each panel being uniform from its base to its upper edge. A primary drawback of these patented deflectors is that they materially reduce drag only at high speeds. Furthermore, it has been found that the fully open tops of these deflectors allow air currents to whip back behind the deflector resulting in increased drag.